A History and Modern Framework for Quality Improvement in Interventional Radiology.

Quality improvement (QI) initiatives have benefited patients as well as the broader practice of medicine. Large-scale QI has been facilitated by multi-institutional data registries, many of which were formed out of national or international medical society initiatives. With broad participation, QI registries have provided benefits that include but are not limited to establishing treatment guidelines, facilitating research related to uncommon procedures and conditions, and demonstrating the fiscal and clinical value of procedures for both medical providers and health systems. Because of the benefits offered by these databases, Society of Interventional Radiology (SIR) and SIR Foundation have committed to the development of an interventional radiology (IR) clinical data registry known as VIRTEX. A large IR database with participation from a multitude of practice environments has the potential to have a significant positive impact on the specialty through data-driven advances in patient safety and outcomes, clinical research, and reimbursement. This article reviews the current landscape of societal QI programs, presents a vision for a large-scale IR clinical data registry supported by SIR, and discusses the anticipated results that such a framework can produce.

Hepatocellular carcinoma locoregional therapies: Outcomes and future horizons.

Hepatocellular carcinoma (HCC) is the most common primary cancer of the liver and has an overall five-year survival rate of less than twenty percent. For patients with unresectable disease, evolving liver-directed locoregional therapies provide efficacious treatment across the spectrum of disease stages and via a variety of catheter-directed and percutaneous techniques. Goals of locoregional therapies in HCC may include curative intent in early-stage disease, bridging or downstaging to surgical resection or transplantation for early or intermediate-stage disease, and local disease control and palliation in advanced-stage disease. This review explores the outcomes of chemoembolization, bland embolization, radioembolization, and percutaneous ablative therapies. Attention is also given to prognostic factors related to each of the respective techniques, as well as future directions of locoregional therapies for HCC.

Nationwide Trends in Tube-Related Genitourinary Interventions for Medicare Beneficiaries.

PURPOSE: To evaluate national trends in tube-related genitourinary interventions, with specific attention to primary operator specialty. METHODS: Using a 5% national sample of Medicare claims data from 2005 to 2015, all claims associated with nephrostomy tube, nephro-ureteral tube, and ureteral stent placement and exchange were identified. The annual volume of the nine billable procedures were analyzed to evaluate trends in the number of procedures performed and primary operator specialty over time. The Charleston Comorbidity Index (CCI) was used to evaluate patient comorbidities and to determine differences in patient populations treated by interventional radiologists and urologists. RESULTS: The total volume of tube-related genitourinary interventions has increased over the course of the study period, representing 455.0 services per 100,000 Medicare Fee-for-Service beneficiaries in 2005 to 607.2 services in 2015, an increase of 33.4%. Interventional radiologists performed the majority of all procedures in all procedure types and for each year (>90%) with the exception of nephro-ureteral catheter placement or ureteral stent placement, for which urologists performed the overwhelming majority of procedures each year (>85%). Interventional radiologists performed 63% of their total number of procedures on patients with a CCI = 3 or higher, and urologists performed 42% of their total number of procedures on patients with a CCI = 3 or higher (P < .01). CONCLUSION: Tube-related genitourinary interventions have demonstrated persistent growth over the 2005 to 2015 decade. Interventional radiologists are the dominant providers for the majority of these interventions compared with urologists while delivering care to a patient population with a higher number of comorbidities.

Characterization of the #Radiology Twitter Conversation During the Global COVID-19 Pandemic.

OBJECTIVE: To assess the #Radiology conversation on Twitter social media platform during the COVID-19 pandemic. MATERIALS AND METHODS: From February 1 to December 31, 2020, all tweets with a #Radiology hashtag were identified using the healthcare social media analytics tool, Symplur Signals. Data collected included number of tweets, retweets, impressions, links, and user characteristics. Data were stratified by the presence of a COVID-19-related keyword, and a social media network analysis was further performed. RESULTS: Of the 68,172 tweets, 10,093 contained COVID-19 content from 2809 users generating 65,513,669 impressions. More tweets with COVID-19 content contained links than without (P < 0.01). Network analysis demonstrated most users were physicians (48.10%), authoring the most tweets (40.38%), using the most mentions (32.15%), and retweeting the most (51.45%). The most impressions, however, were by healthcare organizations not providing clinical care (20,235,547 impressions, 30.89%). Users came from 80 countries, most from the United States (29.3%) and the United Kingdom (8.69%). During early March, COVID-19 dominated the #Radiology conversation, making up 54.67% of tweets the week of March 14 and 64.74% of impressions the week of March 21 compared to 13.97% of tweets and 16.76% of impressions in the remainder of the study period (P < 0.01).There was an influx of new users to the #Radiology conversation during this time period with more users tweeting about COVID-19 than not (P < 0.01). CONCLUSION: Discussion of COVID-19 in the #Radiology community increased significantly during the early weeks of the pandemic. Real time sharing and collaboration proved a useful tool when rapid information dissemination was needed to manage an emerging pathogen.

Locoregional Therapy Approaches for Hepatocellular Carcinoma: Recent Advances and Management Strategies.

Hepatocellular carcinoma (HCC) is the most common primary liver malignancy and third leading cause of cancer-related mortality worldwide. While surgical resection and transplantation are the standard first-line treatments for early-stage HCC, most patients do not fulfill criteria for surgery. Fortunately, catheter-directed and percutaneous locoregional approaches have evolved as major treatment modalities for unresectable HCC. Improved outcomes have been achieved with novel techniques which can be employed for diverse applications ranging from curative-intent for small localized tumors, to downstaging or bridging to resection and transplantation for early and intermediate disease, and locoregional control and palliation for advanced disease. This review explores recent advances in liver-directed techniques for HCC including bland transarterial embolization, chemoembolization, radioembolization, and ablative therapies, with a focus on patient selection, procedural technique, periprocedural management, and outcomes.

Noninvasive Approaches for Anxiety Reduction During Interventional Radiology Procedures.

Periprocedural anxiety is a major cause of morbidity, particularly for interventional radiology procedures that often depend on conscious sedation. Management of anxiety and pain during image-guided procedures has traditionally relied on pharmacologic agents such as benzodiazepines and opioids. Although generally safe, use of these medications risks adverse events, and newer noninvasive, nonpharmacologic techniques have evolved to address patient needs. In this review, we explore the roles of hypnosis, structured empathic attention, anodyne imagery, music, video glasses, and mobile applications in reducing procedural anxiety and pain with the goal of improving patient satisfaction, operational efficiency, and clinical outcomes.

Greenfield stainless steel vena cava filters on computed tomography follow-up.

OBJECTIVE: The objective of this study was to evaluate complications of Greenfield (Boston Scientific, Marlborough, Mass) stainless steel inferior vena cava (IVC) filters on follow-up computed tomography (CT) imaging and to elucidate associated risk factors. METHODS: Ninety-three patients with CT studies obtained for other reasons after Greenfield IVC filter placement (2007-2014) were retrospectively studied. Greenfield filters were placed permanently in those with venous thromboembolism and an expected lifelong contraindication to anticoagulation or life expectancy <6 months. Patients' demographic data, procedural characteristics, and imaging studies were reviewed and factors associated with perforation rates were analyzed. RESULTS: A total of 190 follow-up CT imaging studies were available for review. In total, filter-associated IVC thrombus (n = 10 [10.7%]) and pulmonary embolism breakthrough (n = 4 [4.3%)] were documented by contrast-enhanced CT. Perforation was evident in 18 patients (19.4%) with an average indwelling time of 256 days. No symptomatic perforation and no strut fracture were documented. There was no significant difference in perforation rate with respect to age of the patient (P = .61), sex (P = 1.00), or history of malignant disease (P = .40). The filter perforation rate and number of perforating struts were significantly higher in patients with longer indwelling time (>90 days) than in patients with shorter indwelling time (<90 days; P < .01). Caval cross-sectional areas of patients who experienced IVC filter perforations at >90 days were significantly smaller than those of nonperforated patients (284 vs 358 mm2; P < .01). CONCLUSIONS: Stainless steel Greenfield filters remain a relatively safe option for patients requiring permanent mechanical filtration.

Ultrasound-Accelerated, Catheter-Directed Thrombolysis for Submassive Pulmonary Embolism: Single-Center Retrospective Review with Intermediate-Term Outcomes.

PURPOSE: To evaluate ultrasound-accelerated, catheter-directed thrombolysis (CDT) for treatment of acute submassive pulmonary embolism (PE). MATERIALS AND METHODS: This single-center, retrospective study included patients who underwent CDT for acute submassive PE (N = 113, 52% men/48% women) from 2013 to 2017. Baseline characteristics included history of deep venous thrombosis (12%), history of PE (6%), and history of cancer (18%). Of cohort patients, 88% (n=99) had a simplified PE severity index score of ≥ 1 indicating a high risk of mortality. RESULTS: A technical success rate of 100% was achieved with 84% of patients having bilateral catheter placements. Average tissue plasminogen activator (tPA) therapy duration was 20.7 hours ± 1.5, and median tPA dose was 21.5 mg. Three patients (2.6%) experienced minor hemorrhagic complications. Mean hospital length of stay was 6 days. Mean pulmonary arterial pressure decreased from 55 mm Hg on presentation to 37 mm Hg (P < .01) 1 day following initiation of thrombolytic therapy. All-cause mortality rate of 4% (n = 4) was noted on discharge, which increased to 6% (n = 7) at 6 months. At 6-month follow-up compared with initial presentation, symptom improvements (93%), physiologic improvements (heart rate 72 beats/min vs 106 beats/min, P < .01), oxygen requirement improvements (fraction of inspired oxygen 20% vs 28%, P < .01), and right ventricular systolic pressure improvements by echocardiography (30 mm Hg vs 47 mm Hg, P < .01) were observed. CONCLUSIONS: CDT for acute submassive PE was associated with low complications and mortality, decreased right ventricular systolic pressure, high rates of clinical improvement, and improved intermediate-term clinical outcomes.

Intravascular Ultrasound for the Peripheral Vasculature-Current Applications and New Horizons.

Intravascular ultrasound (IVUS) is a proven and rapidly developing imaging modality that can be used for a multitude of both diagnostic and interventional purposes. By allowing for superior intraluminal characterization, compared with angiography, IVUS has emerged as a technically valuable tool in interventional procedures such as transjugular intrahepatic portosystemic shunt/direct intrahepatic portosystemic shunt, venous interventions (May Thurner stenting, inferior vena cava filter placement, recanalization in the setting of chronic venous thrombosis/insufficiency), percutaneous fenestration in the setting of aortic dissection and angioplasty. Additional applications evaluating coronary arteries and plaque morphology have been described, but are outside the scope of this review. In addition to IVUS's merit as a pre- and intra-procedural guidance modality, there are also several advantages compared to the gold standard of angiography which include decreased need for iodinated contrast, decreased radiation exposure and decreased procedural times in certain cases. With current research, such as that aimed at supraharmonic imaging, further improvements in imaging depth, resolution and contrast to noise ratio are on the horizon.

Primary Care Provider Awareness of IR: A Single-Center Analysis.

PURPOSE: To evaluate primary care provider awareness of interventional radiology (IR) services at a tertiary care academic medical center to identify areas of IR practice that require additional education and awareness initiatives. MATERIAL AND METHODS: An internet-based survey was distributed via email to primary care providers, including internal medicine (IM), family medicine (FM), obstetrics and gynecology (OBGYN), and hospital medicine (HM) physicians in the region. The survey consisted of 17 questions regarding provider demographics, experiences with IR in their practice, awareness of IR training, and awareness of IR procedures and services. RESULTS: A total of 234 of 533 invited physicians completed the survey (40% IM, 22% FM, 22% HM, and 16% OBGYN). Providers rated their knowledge of IR as poor (49, 20.3%), adequate (137, 56.9%), good (49, 20.3%), and excellent (6, 2.5%). Although 235 (97.5%) had consulted IR previously, only 141 (58.5%) had referred a patient directly to IR for an elective procedure. IR was offered as an alternative to surgical procedures never (42, 17.6%), a quarter of the time (101, 42.3%), half of the time (61, 25.5%), three-quarters of the time (27, 11.3%), and every time (8, 3.35%). Most respondents (161, 67.4%) learned the most about IR procedures during residency. Most (180, 75.3%) indicated that they would like to learn more about IR. CONCLUSIONS: These findings indicate that more can be done to educate providers about the potential role of IR in patient care. Provider awareness is limited regarding procedures that are increasingly popular in the IR community. This study helps to identify specific areas of IR in which awareness of can be increased.

Advanced stage breast cancer is associated with catheter-tip thrombus formation following implantable central venous port placement.

PURPOSE: Catheter-tip associated thrombosis is not uncommon in patients with implantable central venous ports; however, the prevalence and clinical impact of this complication on patient management is unclear. This study aims to identify risk factors for thrombus formation in a large population receiving serial echocardiograms (echo) following port placement. METHODS: A total of 396 female breast cancer patients underwent internal jugular vein chest port placement between 2007 and 2013 and received echo studies every third month. Catheter tip position was measured from chest radiography and catheter associated thrombus was identified by echo. RESULTS: Sixteen out of 396 patients (4%) had catheter-tip thrombus. No patients were symptomatic or prophylactically anticoagulated. Patients with thrombus were significantly younger than those without (46.4 years versus 53.4 years, respectively, p = 0.02) and had higher stage breast cancer with 75% versus 44.7% having stage III or IV cancer ( p = 0.017). Thrombus was identified after a median of 91 days. No significant difference was identified in anatomic ( p = 0.1) or measured ( p = 0.15) tip position, port laterality ( p = 0.86), or number of port lumens ( p = 0.65). CONCLUSIONS: In this large cohort, younger patients and those with more advanced stage breast cancer were more associated with catheter-tip-related thrombus after port placement.

Yttrium-90 microsphere selective internal radiation therapy for liver metastases following systemic chemotherapy and surgical resection for metastatic adrenocortical carcinoma.

Adrenocortical carcinoma (ACC) is a rare malignancy with generally poor outcomes and limited treatment options. While surgical resection can be curative for early local disease, most patients present with advanced ACC owing to nonspecific symptoms. For those patients, treatment options include systemic chemotherapy and locoregional therapies including radiofrequency ablation and transarterial chemoembolization. We present the first reported case of utilizing yttrium-90 microsphere selective internal radiation therapy (SIRT) in combination with first line EDP-M (Etoposide, Doxorubicin, Cisplatin, Mitotane) chemotherapy and debulking surgical primary tumor resection for treatment of metastatic ACC. Stable complete radiologic response has been maintained after twelve months with resolution of clinical symptoms. These findings prompt the need for further consideration and studies to elucidate the role of SIRT in combination with systemic and surgical treatment for metastatic ACC.

Outcomes and Direct Costs of Inferior Vena Cava Filter Placement and Retrieval within the IR and Surgical Settings.

PURPOSE: To compare the outcomes and costs of inferior vena cava (IVC) filter placement and retrieval in the interventional radiology (IR) and surgical departments at a tertiary-care center. MATERIALS AND METHODS: Retrospective review was performed of 142 sequential outpatient IVC filter placements and 244 retrievals performed in the IR suite and operating room (OR) from 2013 to 2016. Patient demographic data, procedural characteristics, outcomes, and direct costs were compared between cohorts. RESULTS: Technical success rates of 100% were achieved for both IR and OR filter placements, and 98% of filters were successfully retrieved by IR means, compared with 83% in the OR (P < .01). Fluoroscopy time was similar for IR and OR filter insertions, but IR retrievals required half the fluoroscopy time, with an average of 9 minutes vs 18 minutes in the OR (P = .02). There was no significant difference between cohorts in the incidences of complications for filter retrievals, but more postprocedural complications were observed for OR placements (8%) vs IR placements (1%; P = .05). The most severe complication occurred during an OR filter retrieval, resulting in entanglement of the snare device and conversion to an emergent open filter removal by vascular surgery. Direct costs were approximately 20% higher for OR vs IR IVC filter placements ($2,246 vs $2,671; P = .01). CONCLUSIONS: Filter placements are equally successfully performed in IR and OR settings, but OR patients experienced significantly higher postprocedural complication rates and incurred higher costs. In contrast, higher technical success rates and shorter fluoroscopy times were observed for IR filter retrievals compared with those performed in the OR.

Retrieval characteristics of the Bard Denali and Argon Option inferior vena cava filters.

OBJECTIVE: The purpose of this study was to compare the retrieval characteristics of the Option Elite (Argon Medical, Plano, Tex) and Denali (Bard, Tempe, Ariz) retrievable inferior vena cava filters (IVCFs), two filters that share a similar conical design. METHODS: A single-center, retrospective study reviewed all Option and Denali IVCF removals during a 36-month period. Attempted retrievals were classified as advanced if the routine "snare and sheath" technique was initially unsuccessful despite multiple attempts or an alternative endovascular maneuver or access site was used. Patient and filter characteristics were documented. RESULTS: In our study, 63 Option and 45 Denali IVCFs were retrieved, with an average dwell time of 128.73 and 99.3 days, respectively. Significantly higher median fluoroscopy times were experienced in retrieving the Option filter compared with the Denali filter (12.18 vs 6.85 minutes; P = .046). Use of adjunctive techniques was also higher in comparing the Option filter with the Denali filter (19.0% vs 8.7%; P = .079). No significant difference was noted between these groups in regard to gender, age, or history of malignant disease. CONCLUSIONS: Option IVCF retrieval procedures required significantly longer retrieval fluoroscopy time compared with Denali IVCFs. Although procedure time was not analyzed in this study, as a surrogate, the increased fluoroscopy time may also have an impact on procedural direct costs and throughput.

Role of inferior vena cava filters in transplant patients.

PURPOSE: This study evaluates the selection, use, and risks of permanent and retrievable inferior vena cava filters (IVCFs) in patients who have undergone organ transplantation. MATERIALS AND METHODS: Single-center retrospective review of 35 patients who had an IVCF placed following organ transplantation. Patient demographics, IVCF indication, and eligibility for retrieval were reviewed. Computed tomography (CT) studies showing the filter (n=22) were evaluated independently for IVCF adverse effects. RESULTS: Thirty-two (91%) of 35 patients had retrievable IVCFs placed while three (9%) patients received permanent IVCFs. Filter retrieval was indicated in three of the 32 patients receiving retrievable filters and was performed in two cases. Patients were ineligible for retrieval due to short life expectancy, complications/contraindications to anticoagulation, extended filter dwell time, lost to follow-up, and undetermined therapeutic value of anticoagulation. CONCLUSION: Current practices of filter placement usually dictate placing a retrievable IVCF in transplant patients. However, transplant patients are unlikely to be eligible for filter retrieval especially in situations of advanced age and comorbidities. Given the low incidence of eligibility for retrieval in this patient population, these results suggest preferential placement of permanent filters may reduce the potential morbidity due to filter-related complications, such as strut perforation, in transplant patients.

Cost-benefit analysis of establishing an inferior vena cava filter clinic.

PURPOSE: Adverse events associated with retrievable inferior vena cava filters (IVCFs) have generated an increased interest in improving IVCF retrieval rates to improve patient safety and quality care. This study aims to demonstrate the cost-benefit of implementing an IVCF clinic to improve patient care in an institution in the United States. METHODS: An IVCF clinic was established at a single institution in September 2012 and for ten months referring physicians were contacted to facilitate retrieval when appropriate. Additionally, a retrospective review was conducted on filter placements over the eight preclinic months. Cost-benefit analysis was conducted by creating a model, which incorporated the average cost and reimbursement for permanent and retrievable IVCFs. RESULTS: A total of 190 IVCFs (152 retrievable IVCFs and 38 permanent IVCFs) were implanted during the IVCF clinic period. Twenty-nine percent of the retrievable IVCFs were successfully retrieved compared to 10 of 119 retrievable IVCFs placed during the preclinic period (8.4%). Cost-benefit analysis, using the average of the institution's six most common reimbursement schedules, demonstrated an average net financial loss per permanent or retrievable IVCF not removed. However, a net financial gain was realized for each retrievable IVCF removed. The additional hospital cost to maintain the IVCF clinic was offset by removing an additional 3.1 IVCFs per year. CONCLUSION: An IVCF clinic significantly increases retrieval rates, promotes patient safety, and is economically feasible. Given the adverse event profile of retrievable IVCFs, strategic efforts such as these ultimately can improve quality care for patients with in-dwelling IVCFs.

Design-of-Experiments Approach to Improving Inferior Vena Cava Filter Retrieval Rates.

PURPOSE: The association of retrievable inferior vena cava filters (IVCFs) with adverse events has led to increased interest in prompt retrieval, particularly in younger patients given the progressive nature of these complications over time. This study takes a design-of-experiments (DOE) approach to investigate methods to best improve filter retrieval rates, with a particular focus on younger (<60 years) patients. METHODS: A DOE approach was executed in which combinations of variables were tested to best improve retrieval rates. The impact of a virtual IVCF clinic, primary care physician (PCP) letters, and discharge instructions was investigated. The decision for filter retrieval in group 1 was determined solely by the referring physician. Group 2 included those patients prospectively followed in an IVCF virtual clinic in which filter retrieval was coordinated by the interventional radiologist when clinically appropriate. In group 3, in addition to being followed through the IVCF clinic, each patient's PCP was faxed a follow-up letter, and information regarding IVCF retrieval was added to the patient's discharge instructions. RESULTS: A total of 10 IVCFs (8.4%) were retrieved among 119 retrievable IVCFs placed in group 1. Implementation of the IVCF clinic in group 2 significantly improved the retrieval rate to 25.3% (23 of 91 retrievable IVCFs placed, P < .05). The addition of discharge instructions and PCP letters to the virtual clinic (group 3) resulted in a retrieval rate of 33.3% (17 of 51). The retrieval rates demonstrated more pronounced improvement when examining only younger patients, with retrieval rates of 11.3% (7 of 62), 29.5% (13 of 44, P < .05), and 45.2% (14 of 31) for groups 1, 2, and 3, respectively. CONCLUSIONS: DOE methodology is not routinely executed in health care, but it is an effective approach to evaluating clinical practice behavior and patient quality measures. In this study, implementation of the combination of a virtual clinic, PCP letters, and discharge instructions improved retrieval rates compared with a virtual clinic alone. Quality improvement strategies such as these that augment patient and referring physician knowledge on interventional radiologic procedures may ultimately improve patient safety and personalized care.

Etiology and treatment of acute inferior vena cava thrombosis.

Inferior vena cava thrombosis (IVCT) is a rare but severe disease that is associated with a high rate of mortality. IVCT can be categorized into primary versus secondary thrombosis dependent upon the underlying pathophysiology. The diagnosis includes both clinical probability assessment as well as the imaging evaluation. The optimal therapeutic strategy remains the target of continued research. Although anticoagulation therapy remains fundamental in treating IVCT, its inherent limitations have led to the use of minimally invasive, endovascular treatment options, including transcatheter thrombolysis, mechanical thrombectomy or a combination of these techniques. This review focuses on the etiology, diagnostic assessment, and endovascular treatment options for IVCT.

Conventional versus Drug-Eluting Bead Transarterial Chemoembolization for Neuroendocrine Tumor Liver Metastases.

PURPOSE: To compare outcomes of conventional transarterial chemoembolization with drug-eluting bead (DEB) chemoembolization for treatment of neuroendocrine tumor liver metastases. MATERIALS AND METHODS: This single-center, retrospective study evaluated 177 transarterial chemoembolization treatments (78 conventional chemoembolization treatments using ethiodized oil-based cisplatin, mitomycin C, and doxorubicin and 99 DEB chemoembolization treatments using doxorubicin-loaded 100-300 µm DEBs) from 2012 to 2015. Hepatic disease distribution was 93% bilobar for both groups with largest lesion size 5.0 cm ± 2.7. No difference was noted in regard to lesion size or distribution, carcinoid syndrome, or pancreastatin production. Clinical outcomes including complications; liver function tests (LFTs); and radiologic (modified Response Evaluation Criteria in Solid Tumors), biochemical (pancreastatin levels), and symptomatic responses were evaluated at 1-month follow-up. RESULTS: Higher symptomatic response (complete and partial) was identified with conventional transarterial chemoembolization compared with DEB chemoembolization (47% vs 30%; P < .05). Patients receiving DEB transarterial chemoembolization experienced lower elevation of LFTs (aspartate aminotransferase, 39 U/L vs 122 U/L; alanine aminotransferase, 20 U/L vs 93 U/L; bilirubin, 0.001 mg/dL vs 0.123 mg/dL; P < .05) and less postembolization syndrome (50% vs 67%; P < .05). Patients undergoing first-time DEB transarterial chemoembolization had lower periprocedural octreotide maximum rate requirements (58 µg/h vs 66 µg/h; P < .05). No difference was observed in biochemical (P = .60) or radiologic (P < .20) responses. CONCLUSIONS: Conventional transarterial chemoembolization yields better symptomatic response and may be preferred for patients experiencing carcinoid symptoms. DEB transarterial chemoembolization, with lower LFT elevations and postembolization syndrome incidence, may be preferred for patients with poor liver function.